Volcanic mudflows, called lahars, can cause large amounts of damage to buildings. In this research we developed a method to estimate lahar-induced building damage based on the height, speed and amount of volcanic material in the lahar. This method was applied to a small region in Arequipa, Peru, where computer models were used to estimate the number of buildings affected by lahars. The research found that building location and the size of the flow are most important in determining damage.